Simplify WALSegmentReader.UnmarshalBinary
Simplify WALSegmentReader.UnmarshalBinary

There were two loops over nvals which created some extra allocation
which coudl be replaced with a simplet slice capacity and append.

chenziliang/influxdb,nooproblem/influxdb,chenziliang/influxdb,mark-rushakoff/influxdb,chenziliang/influxdb,influxdata/influxdb,nooproblem/influxdb,linearb/influxdb,runner-mei/influxdb,mark-rushakoff/influxdb,linearb/influxdb,influxdb/influxdb,influxdb/influxdb,linearb/influxdb,influxdb/influxdb,influxdb/influxdb,mark-rushakoff/influxdb,li-ang/influxdb,vladlopes/influxdb,benbjohnson/influxdb,nooproblem/influxdb,runner-mei/influxdb,vladlopes/influxdb,influxdb/influxdb,runner-mei/influxdb,benbjohnson/influxdb,benbjohnson/influxdb,mark-rushakoff/influxdb,runner-mei/influxdb,archsaber/influxdb,li-ang/influxdb,chenziliang/influxdb,influxdb/influxdb,archsaber/influxdb,archsaber/influxdb,linearb/influxdb,nooproblem/influxdb,mark-rushakoff/influxdb,archsaber/influxdb,vladlopes/influxdb,mark-rushakoff/influxdb,nooproblem/influxdb,vladlopes/influxdb,benbjohnson/influxdb,linearb/influxdb,influxdata/influxdb